Tornadoes and hurricanes are the most dangerous storms nature can throw at us. They can destroy entire buildings and cause thousands of injuries or deaths. Most people who live in areas susceptible to these storms keep a close eye on weather reports and take cover or evacuate when one is on the way. Storm chasers keep an even closer eye on weather data, but for a different reason. When a tornado or hurricane happens, they want to be there to observe and record it.

­There are some really good reasons for chasing storms -- mainly, scientific research, though a few people make a living selling photographs or footage of storms. There are also several reasons why amateurs shouldn't go storm chasing, no matter how fun it looks. For one thing, the eight to 12 hours spent driving around with no guarantee of actually seeing a tornado is anything but exciting. But also, storms are very dangerous. Professional storm chasers have meteorological training that allows them to understand the storms they're chasing. They know when conditions are safe and when it's time to back off. They also learn by chasing with other experienced storm chasers. Amateurs should never chase storms. Ever.

We're going to talk to some people who drive thousands of miles to place themselves near tornadoes, some of the deadliest storms in the world. We'll find out why they do it, how they do it and what we can learn from their experiences.

The Nature of the Beast: Tornado Basics

To hunt tornadoes, you need to understand them. A tornado is a swirling mass of air that can reach wind speeds above 300 mph. It's spawned from severe thunderstorms with enough energy and the proper conditions to start a "cyclone" of spinning air. Tornadoes can happen anywhere and at any time, but they tend to happen most frequently in the late evening or during the night, when thunderstorms sweeping across the land have picked up energy from the heat of the day. Tornadoes are most commonly encountered in North America, in a huge area ranging from the Rocky Mountains east to the Atlantic Ocean, and from Mexico into Canada. Ohio, Illinois, Missouri, Kansas, Nebraska, Arkansas, Kentucky, Alabama, Oklahoma and Texas are known for tornadoes, but devastating tornadoes have hit Florida, Pennsylvania and other states.

A tornado can be accompanied by frequent lightning, straight-line winds, heavy rain and hail. All these factors add to the danger of a tornado. The tornado itself causes injury and death in three ways:

Picking people up and hurling them through the air

Crushing people beneath debris

Impaling people with objects flung through the air with incredible force

Des­pite decades of research, we still don't fully understand tornadoes. No one is sure what causes some storms to produce them while other storms don't, or why a few storms produce massive outbreaks of dozens of tornadoes. We do know that they form inside supercells, huge storm clouds that reach up to the stratosphere (an altitude of six miles). Within a supercell, massive quantities of air flow in an updraft. If the horizontal air movement within the supercell is flowing in different directions (wind shear), this could create a spinning effect, known as a mesocyclone. The updraft tilts the mesocyclone so that it is upright, which then allows the updraft itself to start spinning. All the energy within the storm begins to fuel this cyclone. If it touches the ground, it can cause tremendous damage.

Next, we'll check out a day in the life of the people who drive around chasing these dangerous, unpredictable storms.

Measuring Tornadoes

Tornado intensity is measured by the Fujita Scale. Because it's very difficult to measure the wind speed of a tornado as it's happening, and because it's very rare for anyone to be present with the necessary equipment and expertise necessary to even try, we measure them indirectly, based on the damage they do. Certain types of damage are good indicators of the wind speed within the tornado. For example, if a roof is torn off of a modern, well-built home, wind speed is estimated between 156 and 206 mph, a category F3. F0 tornadoes are the weakest, while an F5 tornado is a monster, with winds moving at least 261 mph. There is no such thing as F6 or beyond -- there is technically no upper limit to the F5 category, although scientists don't think it's possible for tornadoes to hit speeds much higher than 320 mph.

Today, meteorologists use an Enhanced Fujita Scale, sometimes referred to as the EF scale. It's basically the same scale, just refined and more detailed.

Storm Chaser on the Hunt

Meteorology students monitor an isolated supercell thunderstorm in Kansas on June 5, 2004.

Storm chasing isn't nonstop action and danger. It's actually a very methodical practice that requires lots of time spent studying weather data, driving, waiting and more driving. Storm chasers can spend 12 hours or more driving around and still not see a tornado of any kind. Byron Turk, navigator for the Discovery Channel's Storm Chasers series, describes the process like this:

We find the storm hopefully before it gets dark, and hopefully it produces a tornado, and hopefully there are roads to it. Lots of decisions need to be made on how the supercell is doing, whether another one is more worthwhile, more data comes in and it's just a constant process of making the right decision over and over again. Hopefully.

In the southern states, storm chasing season runs from March through May. Further north, tornadoes are more common through the summer months [source: National Severe Storms Laboratory]. Storm chasers who don't live in the area will set up camp in a hotel room or other rented space.

Before bed and first thing in the morning, storm chasers check weather reports from the National Weather Service (NWS), looking for favorable tornado conditions. Cold air at high altitudes with warm air close to the ground is a promising sign, along with wind shear, or winds at different altitudes blowing in different directions [source: Trueit]. Areas where cool air masses collide with warm air masses are also tornado spawning grounds. After analyzing the weather data, the chasers select a likely location. Then they hop into their chase vehicle and start driving.

All storm chasers carry radios, phones and computers that allow them to receive a continuous flow of updated weather information. They can look at NWS data or talk to SkyWarn spotters, people scattered across the country who are trained to observe and report storms. At the very least, two people go on a mission -- one can drive while the other checks weather data and tracks the twister.

The chasers may have to drive for several hours just to get to their target location. On the way, weather updates might force them to revise their plan. If they've read the weather data correctly (and with a little luck), they'll find themselves within visual distance of a storm. Once they spot towering cumulonimbus clouds, they'll know they're on the right track. The storm chasers zero in on the storm while listening to SkyWarn reports. These reports can pinpoint a specific location where a tornado or conditions known to produce tornadoes have already been spotted. Another important clue: NWS issues a tornado watch or tornado warning for an area.

As they close in on the storm, the chasers will watch for several elements. One is the counterclockwise rotation of clouds typical of a supercell, evidence of strong air currents within the storm. Another is a wall cloud, a cloud that seems to descend from the bottom of the storm. Wall clouds don't always produce tornadoes, but they're a sign that one might be forming.

At this point, the chasers might have time to look for a good place to observe the tornado. Ideally, they would set up on a hill about three miles away to get the best view [source: Trueit]. Once a funnel cloud forms and a tornado touches ground, one of the chasers will track its movement by watching it against a stationary background object. A tornado can change directions suddenly, but in general the storm chasers will make sure they can move perpendicular to its path to get away if they need to.

In the next section, we'll look at the equipment storm chasers use.

Hurricane Hunters

Most of the time, when we talk about storm chasers, we're talking tornado chasers. There are people who track and even enter hurricanes, but no one really has to "chase" a hurricane. If there's a hurricane going on, you'll know where to find it.

People have been flying planes right into hurricanes since World War II. The key is high altitude. The severe winds throw planes around in seemingly random directions, sometimes thousands of feet at a time. If the plane was flying too low, it could easily be slammed down into the sea or land. By flying inside the hurricane, meteorologists can get extremely accurate measurements of the conditions there. They can also fly above the hurricane and drop weather instruments down into it.

Basic Storm Chaser Gear

Equipment used by storm chasers can range from basic (digital camera, cell phone) to amazing custom-built machines and research devices (TIV2, Doppler On Wheels). Let's strip it down to a storm chaser's bare essentials:

Video camera - Documentary crews are equipped with the latest HD cameras (or even IMAX), often with multiple camera operators to capture additional angles. But every storm chaser wants to record the storms he or she spots, so even the most budget-conscious chaser has a video camera along for the ride.

Digital camera - A still camera can capture details of a storm that videos often miss. Digital photos can also be uploaded quickly and easily to the Internet for other storm enthusiasts to see.

Laptop computer - With a cell phone, a laptop can maintain a continuous Internet connection, allowing for constantly updated weather data, including weather maps and other details that a weather radio can't provide.

Radios - If the storm chasers are riding in multiple vehicles, they can use walkie-talkies to stay in contact. SkyWarn members often use ham radios to communicate their observations, so chasers will need one to listen in. CB radios can bring in info from truckers who may have experienced nearby storms. A police scanner is useful for hearing the radio traffic of emergency crews who may be preparing for or heading to the aftermath of a tornado.

Food and drink - A day of storm chasing means lots of time in a car. A sandwich and some coffee are pretty crucial to any chaser team's success.

On the next page, let's dive into the high-tech, expensive stuff.

The First Storm Chaser

There were a few notable storm chasers in the 1950s and '60s, like Roger Jensen. The very first storm chaser, however, may have been the person who took a famous photograph of a tornado in South Dakota. The photo shows a massive storm cloud with a thick tornado descending to the ground, kicking up a huge debris cloud. Two smaller tornadoes extend out from the cloud to either side, like devil's horns. The date was Aug. 28, 1884, and the image is the first known photo of a tornado [source: Rosenfeld].

Advanced Storm Chaser Gear

Weather-monitoring computer equipment during a storm chasing tour in Nebraska

Meteorologists have constructed special vehicles loaded with weather detection equipment and have even designed devices intended to be sucked into a tornado, where they could gather information.

The Totable Tornado Observatory (TOTO) was one of the first tornado observation devices, built by the National Severe Storms Laboratory in 1981. It was basically an oil drum packed with scientific instruments. It could be left in the path of an oncoming tornado, where it would collect information about conditions as the tornado passed over, or even from within the tornado itself. TOTO never actually got into a tornado, unfortunately.

Other attempts to gather data from the inside of a tornado include smaller versions of TOTO, such as Dillo-cam. One experiment involved firing rockets into a tornado from an airplane!

Doppler On Wheels (DOW) is a vital component for advanced storm chasers. It's the same technology used to create the radar weather maps you see on your local news, but mounted to the back of a truck. This gives the chasers immediate, on-the-spot info about weather conditions. In 1999, a DOW truck recorded the world record tornado wind speed, 318 mph, in Oklahoma [source: World Book].

A few storm chaser crews deploy their own radiosondes. These are weather balloons. When released, they rise through the atmosphere, recording air pressure, wind speed and direction, and temperature data.

The most amazing storm chaser gear comes in the form of chaser vehicles. These range from simple modifications like additional batteries to power all the computers and radios, to the outlandish TIV2, which looks like something that drove straight out of "The Road Warrior."

TIV stands for Tornado Intercept Vehicle. The first TIV was a heavily modified pickup truck. You can learn all about it in How the Tornado Intercept Vehicle Works. TIV2 is an even more radical design. The truck is heavily reinforced and weighs roughly eight tons [source: Discovery Storm Chasers blog]. The weight makes it harder (but not impossible) for a tornado to lift. It has hydraulic jacks that extend body panels down to the ground, preventing tornadic winds from getting underneath the truck. The truck can also extend stabilizing jacks down to the ground. Lots of electronic gear, including weather and communications equipment, is wired directly into the dashboard. The windows are designed to give camera operators the best possible view of an incoming storm.

Up next, we'll try to figure out why people do this sort of thing.

Why Chase Storms?

Near Woonsocket, S.D., a storm chaser plants a weather probe in the path of a tornado.

What could possibly drive people to place themselves near these dangerous storms? There are a few reasons.

Fun and excitement - It's probably a bad idea to go out and chase storms just for kicks, but these are definitely driving factors for many chasers. In fact, some companies offer storm chasing tours. After paying a fee, the "storm tourists" get to go on a chase with experienced guides. That's definitely a better idea than chasing a storm on your own.

Profit - There are some people who make a living selling footage and images they capture of storms. There's no doubt about it, tornadoes are amazing and people love seeing them, as long as they aren't bearing down on their home. Warren Faidley is one of the more well-known storm chasers -- in fact, he bills himself as "the world's only professional storm chaser." His photos of storms can sell for five figures. Other chaser teams make a living filming documentaries about tornadoes, like the crew from the Discovery Channel's Storm Chasers TV series.

Research - Most storm chasers collect weather data when they get close to a tornado. They may have other motivations, but at the heart of every storm chaser in an insatiable curiosity about these awe-inspiring storms. Understanding tornadoes doesn't just satisfy our curiosity, it helps us react to storms with better, more accurate tornado warnings. The result: tornado deaths in the U.S. have declined since the 1960s, despite an overall increase in the number of tornadoes [source: NSSL].

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Members of S.T.E.P.S. (Severe Thunderstorm Electrification and Precipitation Study) launch a weather balloon into a tornadic supercell thunderstorm.

Community and friendship - Storm chasing is like any other hobby. Chasers become close friends. In fact, because they work together during some very intense experiences, they often develop a very close bond. "Chasing tornadoes is a gritty, down-and-dirty adventure with a solid group of people whom I feel a close bond with," said Byron Turk. "I've made some very good friends from the adventures. What success we achieve is all the more sweet after suffering through several days of 12-hour drives, nearly no sleep, wearing the same clothes that smell 2 weeks riper than they should. We have a goal and it is a very difficult one to achieve. There's a sense of pride in that."

So what have we learned about tornadoes in the last few years? Meteorologists have zeroed in on the conditions that cause them. We still don't know exactly when and where a tornado will form, but we're getting closer. Each time a storm chaser gets close to a tornado, another piece is added to the puzzle. A Discovery Channel crew captured footage of "minitornadoes" revolving within the main tornado in 2007. Later, computer modeling used this information to develop a more accurate picture of tornado formation and life cycle [source: Storm Chasers blog]. People once thought that tornadoes were simply smaller versions of hurricanes, an idea that seems laughable now. Yet modern examinations of supercell air currents reveal large-scale cyclonic action -- big thunderstorms swirl in a way not unlike that of a hurricane [source: Rosenfeld].

In addition to prediction, scientists are puzzled by several other aspects of tornadoes. One important mystery: Why do they develop such incredible wind speeds? Every thunderstorm contains enormous quantities of energy, energy on such a scale that they are compared to nuclear weapons. How that energy is sometimes converted to whirling wind speeds above 300 mph is still a mystery.

For more stuff on tornadoes, hurricanes and all kinds of natural disasters, try the next page.

The Twister Sisters

Peggy Willenberg and Melanie Metz (they're not actually related) are a storm chasing duo from Minnesota. They provide storm coverage for several news organizations, and also promote storm chasing tours. Although neither is a professional meteorologist, they both have meteorological training to the extent that they give presentations at conferences and conduct weather workshops. The Twister Sisters stand out among the usual "boys club" storm chasers, but they've never gone storm chasing with Dee Snider.